blood trans Flashcards
what class are antibodies
IgM class,
what temp are they active at
reactive at 37ºC
why must the correct blood type br transfered
capable of fully activating complement, so are able to cause potentially fatal haemolysis (destruction of red cells) if incompatible blood is transfused.
what are the blood types
a
b
ab
o
what are the antigens on each
a- a antigen
b- b antigen
ab - both
o - no antigen, H stem only
having a type blood what antibodies would be present in the plasma
anti b
and if you had b type
anti a
if you had ab
no antibodies
if o
anti a and anti b
how are ab antigens on red blood cells formed
dding one or other sugar residue onto a common glycoprotein and fucose stem (H antigen) on the red cell membrane.
how are antigen determined
by corresponding genes:
what does the a gene code for
The A gene codes for an enzyme that adds N-acetyl galactosamine to the common H antigen
and b gene codes for
- The B gene codes for enzyme which adds galactose
both ab antigens are said to b e
A and B genes are co-dominant
what is the o gene said to be
O gene is recessive
If a person is blood group A - genes could be AA or OA
in a lab what can you see if teh wrong blood is given
agglutination, clumped
what is the Rh system based on
antigen D
what r the blood groups
Blood groups: RhD positive (if have D antigen) or RhD negative (if not).
explain what the genes cause
D gene codes for D antigen on red cell membrane.
d gene codes for no antigen and is recessive (no actual antigen).
Therefore:
Group RhD negative = dd
Group RhD positive = DD or Dd
what do p People who lack the RhD antigen (ie: RhD negative) create
CAN make anti-D antibodies AFTER they are exposed to the RhD antigen - either by transfusion of RhD positive blood, or in women if they are pregnant with an RhD positive foetus
what class are anti D antibodies
Anti-D antibodies are IgG class antibodies.
Implications of anti-D antibodies:
Future transfusions– the patient must in future, have RhD negative blood (otherwise their anti-D would react with RhD positive blood - causes delayed haemolytic transfusion reaction– with anaemia; high bilirubin (from breakdown of red cells); jaundice etc.).
HDN
what is HDN
haemolytic disease of the newborn- if RhD neg mother has anti-D, then in the next pregnancy, if fetus is RhD positive: mother’s IgG anti-D antibodies can cross the placenta (only IgG class antibodies can do this) – attach to the RhD positive red cells of the foetus and cause haemolysis of foetal red cells - if severe: hydrops fetalis and death. If less severe, the baby survives but after birth, the high bilirubin levels can cause brain damage or death.
if it is less severe will the baby die
no survives after birth , but high bilirubin levels cab cause brain damage an death
you must
Transfuse blood of same RhD group (no harm to give RhD negative to a positive patient - just wasteful!
what blood can you give to anyone
Group O negative blood (i.e. Rh D negative)
are there any other antigens
yes, behshamar
Once patients have formed an antibody, we must use corresponding antigen negative blood; or else there is a risk of a delayed haemolytic reaction.
how to check abo and rhd compatibility
antibody screen
function of antibody screen
exclude any clinically significant immune antibodies:
how it works
Patient plasma is incubated with 2 or 3 different fully typed ‘screening’ red cells, which are known to possess all the blood group antigens which matter clinically.
if negative
any donor blood which is ABO & RhD compatible can be given.
if positive
the antibody must be identified with the use of a large panel of red cells. Donor units of blood that lack the corresponding blood group antigen are then chosen for cross matching with the recipient’s plasma prior to transfusion.
sumarise compatabillity
1. Patient blood sample (plasma + cells).
ABO group (test patient’s red cells with known anti-A and anti-B reagents). RhD group (test patient’s red cells with known anti-D and reagent). Select donor blood of the same ABO & RhD group. Antibody screen +/- antibody panel, to identify antibody/ies.
2. Cross-match: patient’s serum mixed with chosen donor red cells - should not react: if reacts (agglutinates) = incompatible.
what tests di blood donor go thru
- Group & screening:
2. Infection testing:
what is Prion Disease
Prion proteins have been found in membranes of lymphocytes and platelets and the prions of variant Creutzfeldt-Jacob disease (CJD) are found in lymphoreticular tissues
A blood test to exclude any donor with vCJD is not yet available
is the whole blood given
no, just the part they require
e.g. only platelets and factor 8
risk of at risk of fluid overload, for patient a red cell transfusion for anaemia
